Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS7052750 B2
Publication typeGrant
Application numberUS 10/633,934
Publication dateMay 30, 2006
Filing dateAug 4, 2003
Priority dateAug 9, 2002
Fee statusPaid
Also published asDE10236502A1, DE10236502B4, DE50305327D1, EP1388415A1, EP1388415B1, EP1388415B2, US20040067382
Publication number10633934, 633934, US 7052750 B2, US 7052750B2, US-B2-7052750, US7052750 B2, US7052750B2
InventorsRalf Niepelt
Original AssigneeNordenia Deutschland Gronau Gmbh
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Sealable film for tear-open packaging
US 7052750 B2
Abstract
A sealable film is used for the production of tear-open packages. The film, as a monofilm, in total, or as a multi-layer laminate film, produced by means of coextrusion, has at least in one layer a polymer mixture of a cycloolefin copolymer (COC) and polyolefin or an ethylene copolymer, whereby the COC portion in the polymer mixture is 10 to 80 wt.-%, the remainder polyolefin or ethylene copolymer. Packages produced from such films demonstrate balanced tear start and tear propagation properties in the crosswise and lengthwise direction of the film.
Images(4)
Previous page
Next page
Claims(16)
1. A tear open package made of a multi-layer coextruded sealable film with balanced tear start and tear propagation properties of the tear open package in crosswise and lengthwise direction of the film wherein said film has three layers namely a core layer formed from a polyolefin, and on each side of said core layer an adjacent layer forming an outside layer which comprises a polymer mixture of
a) 20 to 80 wt. % cycloolefin copolymer (COC) and
b) remainder a member selected from the group consisting of a polyolef in and an ethylene copolymer.
2. The tear open package according to claim 1, wherein said core layer has a core layer thickness and each adjacent layer forming an outside layer has an outside layer thickness, said core thickness being a multiple of the outside layer thickness.
3. The tear open package according to claim 1, wherein the cycloolefin copolymer is an ethylene/norbornene copolymer produced using a metallocene catalyst.
4. The tear open package according to claim 1, wherein said member is a linear low-density polyethylene.
5. The tear open package according to claim 1, wherein said member is a polypropylene.
6. The tear open package according to claim 1, wherein said film has a thickness of least 15 μm.
7. The tear open package according to claim 1, wherein said film is produced by a flat film extrusion process or an extrusion blowing process.
8. The tear open package according to claim 1, wherein before further processing, said film is subjected to a finishing process selected from the group consisting of lamination, imprinting, and coating.
9. A tear open package made of a coextruded sealable film with balanced tear start and tear propagation properties of the tear open package in crosswise and lengthwise direction of the film wherein said film has three layers namely first and second outside layers and one core layer wherein said first outside layer is formed from a polyolefin, said second outside layer comprises a polymer mixture of
a) 20 to 80 wt. % cycloolefin copolymer (CCC) and
b) remainder, a member selected from the group consisting of a polyolef in and an ethylene copolymer
and said core layer is formed from a polymer mixture of cycloolefin copolymers and polyolefins having a polyolefin content less than said first outside layer and greater than said second outside layer.
10. The tear open package according to claim 9, wherein said core layer has a core layer thickness and each of said first and second layers has an outside layer thickness, said core layer thickness being a multiple of the outside layer thickness.
11. The tear open package according to claim 9, wherein the cycloolefin copolymer is an ethylene/norbornene copolymer produced using a metallocene catalyst.
12. The tear open package according to claim 9, wherein said member is a linear low-density polyethylene.
13. The tear open package according to claim 9, wherein said member is a polypropylene.
14. The tear open package according to claim 9, wherein said film has a thickness of least 15 μm.
15. The tear open package according to claim 9, wherein said film is produced by a flat film extrusion process or an extrusion blowing process.
16. The tear open package according to claim 9, wherein before further processing, said film is subjected to a finishing process selected from the group consisting of lamination, imprinting, and coating.
Description
CROSS REFERENCE TO RELATED APPLICATIONS

Applicant claims priority under 35 U.S.C. 119 of German Application No. 102 36 502.4 filed Aug. 9, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the use of a sealable film for the production of tear-open packaging.

2. The Prior Art

Conventional blown films or flat films have very different mechanical properties in the lengthwise and the crosswise direction. While films made of polypropylene preferably tear in the machine running direction, tears in polystyrene films preferably propagate themselves crosswise to the machine running direction. The anisotropic mechanical properties are a disadvantage when these films are used as film packaging. When a film package is opened, there is the particular problem that the film package tears open in an uncontrolled manner.

Furthermore, cycloolefin copolymers are known as film materials (Verpackungs-Rundschau 9/18, pages 52 to 54). The raw material basis for cycloolefin copolymers is ethylene and dicyclopentadiene, from which the comonomer norbornene is obtained. Cycloolefin copolymers, abbreviated as COC, are produced from norbornene by solvent polymerization with ethylene, using metallocene catalysts. Cycloolefin copolymers are amorphous, relatively rigid and brittle, highly transparent plastics, the glass transition temperature of which can be modified by means of the installation ratio of ethylene and norbornene. Because of the brittle character of the polymers, the films possess a low tendency to tear and tend to break if they are bent severely. The mechanical properties of these materials can be modified by mixing them with polyolefins.

Deep-drawable laminate films, which have a layer of cycloolefin copolymer and at least one layer made from a polyolefin, are known from EP 1 213 138 A1. The connection between the COC layer and the polyolefin layer is produced by means of an adhesion agent, e.g. on the basis of a linear polyethylene.

SUMMARY OF THE INVENTION

The object of the invention is to provide a sealable film for the production of tear-open packaging, which does not tear open in an uncontrolled manner when the packaging is opened.

These and other objects are achieved in accordance with the invention by the use of a sealable film for the production of tear-open packages that demonstrate balanced tear start and tear propagation properties in the crosswise and lengthwise direction of the film. The film, which may be a monofilm or single layer film in total, or a multi-layer laminate film produced by means of coextrusion, has at least one layer of a polymer mixture of a cycloolefin copolymer (COC) and polyolefin or an ethylene copolymer. The COC portion in the polymer mixture is 20 to 80 wt.-%, the remainder polyolefin or ethylene copolymer.

Preferably, an ethylene/norbornene copolymer produced using metallocene catalysts is used as the cycloolefin copolymer. Mixing of the cycloolefin copolymer preferably takes place with a low-density polyethylene having a linear structure, particularly linear low-density polyethylene (LLDPE) or very low-density polyethylene (VLDPE). Furthermore, ethylene copolymers, e.g. ethylene/vinyl acetate copolymer (EVA), ethylene/butyl acrylate copolymer (EBA), ethylene/acrylic acid copolymer, (EAA) and the like are suitable for mixing. For tear-open packaging that is exposed to higher temperatures, polypropylene is preferably used for mixing with COC.

According to the invention, advantage is taken of the fact that a film which, as a monofilm, in total, or as a multi-layer laminate film, produced by means of coextrusion, contains at least in one layer a polymer mixture of COC and a polyolefin, demonstrates balanced mechanical properties in the lengthwise and crosswise direction of the film, and particularly possesses balanced tear start and tear propagation properties. A tear that occurs when the film is torn open propagates in a straight line, in each instance, both in the lengthwise direction of the film and the crosswise direction of the film. Packaging produced from this material, e.g. in the form of bags, can therefore be opened without having the packaging tear in an uncontrolled manner. Perforations or tear notches are not necessary. In addition, the film has good rigidity and therefore punchability and cuttability, and is easy to seal if the proportion of polyolefin is sufficient.

According to a preferred embodiment of the invention, sealable laminate films that have at least three layers are used to produce tear-open packaging. The laminate film can have a core layer made from a polyolefin and layers adjacent to the core layer on both sides made from polymer mixtures of cycloolefin copolymers and polyolefins. One outside layer may contain a polyolefin, as a sealing layer, and the other outside layer may be formed from a cycloolefin copolymer or a polymer mixture having a high cycloolefin copolymer proportion. For the intermediate layers, polymer mixtures of cycloolefin copolymers and polyolefins may be used that have a polyolefin content between the values in the outside layers. The polyolefin content changes, step by step, from a high value at the sealing layer to a low value at the opposite layer, the properties of which a re marked by the high COC proportion. According to a particularly preferred embodiment of the invention, the film possesses a three-layer structure, whereby the thickness of the core layer, which is a polyolefin or a polymer mixture with a high polyolefin content, is a multiple of the thickness of the two outside layers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

film that is used to produce tear-open packaging in accordance with the invention has a thickness of at least 15 μm and can be produced by means of a flat film extrusion process or an extrusion blowing process. The film can be further finished by means of lamination, imprinting, or coating, e.g. with aluminum coatings, before being processed further.

Exemplary Embodiments

The following exemplary embodiments relate to three-layer laminate films produced by means of coextrusion, having a symmetrical layer structure A-B-A or an asymmetrical layer structure A-B-C.

EXAMPLE 1

The laminate film has a total thickness of 70 μm and has a symmetrical layer structure A-B-A with

Layer A: 10 μm

80 wt.-% cycloolefin copolymer

20 wt.-% polyethylene LLDPE C8

Layer B: 50 μm

100 wt.-% polyethylene LLDPE C8

EXAMPLE 2

The laminate film has a total thickness of 50 μm and has a symmetrical layer structure A-B-A with

Layer A: 7 μm

80 wt.-% cycloolefin copolymer

20 wt.-% polyethylene LLDPE C8

Layer B: 36 μm

100 wt.-% polyethylene LLDPE C8

EXAMPLE 3

The laminate film has a total thickness of 50 μm and has an asymmetrical layer structure A-B-C with

Layer A: 7 μm

80 wt.-% cycloolefin copolymer

20 wt.-% polyethylene LLDPE C8

Layer B: 36 μm

20 wt.-% cycloolefin copolymer

80 wt.-% polyethylene LLDPE C8

Layer C: 7 μm

100 wt.-% polyethylene LLDPE Ci

The films according to the exemplary embodiments possess balanced mechanical properties in the lengthwise and crosswise direction, particularly balanced tear start and tear propagation properties. The following mechanical properties were measured in the machine direction, i.e. lengthwise direction MD, and the crosswise direction CD:

Example Example Example
1 2 3
Tear MD mN 10001400 400600 250450
propagation
properties
according to
Elmendorf CD mN 10001400 400600 250450
ISO 6383-2
Strengths MD N/inch 4050 2535 2333
DIN 53455 CD N/inch 4050 2535 2333
Modulus of MD N/mm2 500600 500600 450550
elasticity
DIN 53455 CD N/mm2 450550 500600 450550
Stretching MD % 400600 300500 150350
DIN 53455 CD % 400600 300500 150350
Yield stress MD N/inch 3040 2030 1525
DIN 53455 CD N/inch 3040 2030 1525
Strengths at X 3% MD N/inch 2232 188  1525
% stretching
DIN 53455  5% MD N/inch 2838 2232 1525
10% MD N/inch 3040 2535 1626
 3% CD N/inch 2232 1828 1323
 5% CD N/inch 2838 2232 1525
10% CD N/inch 3040 2535 1626

It was possible to produce packaging bags that were easy to open and demonstrated balanced tear start and tear propagation properties in the lengthwise and crosswise direction from all the films.

While only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5532030 *May 26, 1995Jul 2, 1996Mitsui Petrochemical Industries, Ltd.Polyolefin multilayer laminate, vessel and packaging material
US5561208 *Aug 2, 1995Oct 1, 1996Nippon Zeon Co., Ltd.Medical implement, polymer composition, and optical material
US5846620 *Feb 6, 1997Dec 8, 1998W. R. Grace & Co.-Conn.High strength flexible film package
US5912070 *Apr 9, 1997Jun 15, 1999Mitsui Chemicals, Inc.Laminated film and packaging material
US6030255 *Jan 31, 1996Feb 29, 2000Nippon Zeon Co., Ltd.Insulator and high frequency connector
US6165573 *Jul 4, 1995Dec 26, 2000Mitsui Petrochemical Industries LtdMulti-layer laminates and uses thereof
US6310160 *Sep 29, 1997Oct 30, 2001Nippon Zeon Co., Ltd.Norbornene polymer and process for preparing the same
US6767966 *Feb 22, 2001Jul 27, 2004Ticona GmbhPolymer mixture containing an amorphous polyolefin which contain cycloaliphatic olefins
US20010014384 *Feb 28, 2001Aug 16, 2001Masahiro KishineMultilayer film for packaging
US20030170479 *Jun 13, 2001Sep 11, 2003Herbert PeifferWhite, sealable, thermoformable, biaxially oriented and coextruded polyester film containing a cyclooelfin copolymer, method for producing the same and the use thereof
US20040067382 *Aug 4, 2003Apr 8, 2004Ralf NiepeltSealable film for tear-open packaging
US20040142195 *Aug 5, 2003Jul 22, 2004Roberts William P.High free shrink, high modulus, low shrink tension film with elastic recovery
EP0120562A2 *Jan 26, 1984Oct 3, 1984Exxon Research And Engineering CompanyElastomer, polypropylene blends for optically clear products
EP1213138A1Dec 6, 2001Jun 12, 2002Huhtamaki Deutschland GmbH & Co. KGProcess for making a multilayered film
EP1300238A2 *Sep 5, 2002Apr 9, 2003Flexopack S AMultilayer packaging film and process
JPH08165357A * Title not available
Non-Patent Citations
Reference
1Verpackungs-Rundschau Sep. 1998, pp. 52 to 54.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US8551587Sep 27, 2012Oct 8, 2013Exxonmobil Oil CorporationUniaxially shrinkable, biaxially oriented polypropylene films
WO2013055461A1Aug 30, 2012Apr 18, 2013Exxonmobil Oil CorporationSqueezable and conformable oriented polypropylene label
WO2013058881A1Sep 5, 2012Apr 25, 2013Exxonmobil Oil CorporationSoft multi-layer shrink films
WO2013066536A1Sep 27, 2012May 10, 2013Exxonmobil Oil CorporationUniaxially shrinkable, biaxially oriented polypropylene films
Classifications
U.S. Classification428/35.7, 428/516
International ClassificationC08J5/18, B65D75/58, B32B27/32
Cooperative ClassificationC08J5/18, B65D75/58, B32B27/32, C08J2365/00
European ClassificationC08J5/18, B32B27/32, B65D75/58
Legal Events
DateCodeEventDescription
Nov 22, 2013FPAYFee payment
Year of fee payment: 8
Nov 26, 2009FPAYFee payment
Year of fee payment: 4
Jun 25, 2004ASAssignment
Owner name: NORDENIA DEUTSCHLAND GRONAU GMBH, GERMANY
Free format text: CORRECTION OF ASSIGNMENT RECORDED ON NOVEMBER 10, 2003 AT REEL 014676 FRAME 0467;ASSIGNOR:NIEPELT, RALF;REEL/FRAME:015501/0317
Effective date: 20030916
Nov 10, 2003ASAssignment
Owner name: NORDENIA DEUTSCHLAND GRONAU GMBH, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NIEPELT, RALPH;REEL/FRAME:014676/0467
Effective date: 20030916